## The U combinator

The U combinator allows you to define recursive functions and I think it is simpler to understand than the Y combinator.

The U combinator allows you to define recursive functions and I think it is simpler to understand than the Y combinator.

Why you can’t see the Apollo lunar landing sites from Earth.

Physicists seem still to be taught about tensors as being, essentially, multidimensional arrays with special transformation rules which must be learned by rote. So I wrote a document which tries to present a more useful approach.